The present invention relates generally to an apparatus for the transmission and reception of power line carrier signals and, more particularly, to an apparatus that has common components which cooperate to both transmit and receive modulated carrier frequencies.
The superimposition of carrier signals on power lines for the purpose of communicating digital data from one location to another is a technique that is known to those skilled in the art. When a particular communication station, within a carrier signal communications network, is intended to both receive and transmit modulated signals, that station is usually provided with separate transmitting and receiving circuits. When, for purposes of size or cost reduction, the transmitter and receiver are designed to utilize common components, conventional linear audio amplifier techniques are generally avoided because of the assumption that the use of these techniques would be too costly in the design of a transmitter for power-line communications.
U.S. Pat. No. 4,323,882, which issued to Gajjar on Apr. 6, 1982, discloses an apparatus and method for inserting carrier frequency signal information on a distribution transformer's primary winding. It provides power line carrier frequency signals at the distribution transformer's primary winding by controlled current injection onto the neutral and phase conductors of the distribution transformer is secondary winding. The resulting carrier signal can then be modulated, by any one of a number of known methods, to communicate digital data along the power lines to a receiver at a remote location. U.S. Pat. No. 2,883,459, which issued to Roy on Apr. 21, 1959, discloses a carrier current intercommunication system which utilizes a circuit arrangement that acts both as a transmitter and a receiver. Similarly, U.S. Pat. No. 2,342,787, which issued to Brown on Feb. 29, 1944, provides a carrier current transmission system which utilizes circuit arrangements for the transmitter and receiver which are simple and low cost.
U.S. Pat. No. 3,495,217, which issued to Brooks on Feb. 10, 1970, discloses an integrated semiconductor circuit for both transmitting and receiving digital information. This particular invention combines its transmission and reception circuitry in one unit which is capable of transmitting and receiving pulse information on a transmission line. U.S. Pat. No. 2,936,367, which issued to Kobetich on May 10, 1960, discloses a transceiver which is capable of acting as an amplifier under one set of conditions and functioning as a detector under another set of conditions.
It is advantageous for a transceiver to be small in size and low in cost while also being able to reliably perform its functions. A significant reduction in the transceiver's size and cost also permits its inclusion in various apparatus which, themselves, are relatively small such as electric power meters intended for use in private residences.